2 replies to this topic

[chemengstudents]

I have a combustion process, and have calculated the net enthalpy of my inlets and outlets. Some of the energy released by the combustion is used to heat a cooling stream, maintained at temperature 46degC.

 

I wish to calculate the power required to maintain this cooling stream temperature: I was thinking of integrating the specific heat capacity of the water, with respect to temperature, and multiplying by the mass flowrate of the cooling stream.

 

Would this give the power required to maintain the coolant stream at 46degC or am I incorrect?

 

Thanks.

[Art Montemayor]

You have a communication problem.  Power, as expressed in engineering applications is the energy rating of an energy provider (hydro electric dam, electric generator) or driver (engine, electric motor).

 

Do you mean to state the heat transfer rate into the water stream you propose to heat up?  Also, what do you mean by "calculated the net enthalpy of my inlets and outlets"?  Inlets and outlets of WHAT?   The way to solve a problem is to understand it.  The reason you are not sure of the method of solution may be because you don't understand the problem.

 

If all you want to know is how much heat transfer (Btu/hr, or kcal/hr) are required to heat up you water, then all you have to do is to use:

 

Q  = W Cp (T₂-T₁)

where,

Q = the heat transferred in a heat exchanger

W = mass flow rate of the water

Cp = the specific heat of the water at constant pressure

T₂ = the outlet temperature of the water (46 ^oC)

T₁ = the initial temperature of the water entering the heat exchanger.

[chemengstudents]

Thanks very much for this reply. I was being stupid and over-complicating the problem.